A146778 - OEIS

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A146778 as a simple table

n	a(n)
1	1
2	1
3	1
4	1
5	1
6	5
7	17
8	43
9	145
10	633
11	4131
12	31831
13	267243
14	2665825
15	33726547
16	521722083
17	9834245987
18	228276099483
19	6476476460303
20	221310304612835
21	9127636122908961

[1,1,1,1,1,5,17,43,145,633,4131,31831,267243, 2665825,33726547,521722083,9834245987, 228276099483,6476476460303,221310304612835, 9127636122908961]